I have tried out rooUPnP into Naim NAC272 and find it to work well.
It runs at 192,000 and 24 Bit PCM.
Thanks for pointing out FLAC setting above as I was getting static through system which had previously been setup for LMS2UPnP.
The setup is very easy and much more straightforward than LMS2UPnP set up because there is no need to get hands dirty using terminal editor etc. It is so easy and can be recommended to less computer literate users who can assemble a Raspberry Pi.
Issues I found are the same as @Trickydickie ie issues with discovery when various endpoints disappear and sometimes reappear, the whole extension disappearing then reappearing on the extension page.
Also playback of 192k files disrupting the queue which is believed to be a Naim issue.
I would have tried Sonos Port, AMP and speakers but I have 12 appearing as rooUPnP in the Squeezebox listing is devices, all with identical description so I cannot identify which is which. It would be useful if either the name could be pulled through from the extension where they are identified by name or preferably (in my case) being able to disable the unwanted items in the extension.
Trust this feedback helps.